Several leaders of the Islamic State group in Iraq have been killed in US air strikes in recent weeks, dealing a blow to the jihadist forces, the Pentagon said Thursday.

“I can confirm that since mid-November, targeted coalition airstrikes successfully killed multiple senior and mid-level leaders” in the IS, spokesman Rear Admiral John Kirby said in a statement.

“We believe that the loss of these key leaders degrades ISIL’s ability to command and control current operations against Iraqi Security Forces, including Kurdish and other local forces in Iraq,” said Kirby, using an alternative acronym for the jihadists.

“While we do not discuss the intelligence and targeting details of our operations, it is important to note that leadership, command and control nodes, facilities, and equipment are always part of our targeting calculus,” he said.

The strikes showed “the coalition’s resolve” in helping Iraqi forces take on the IS group, he said.

The bombing raids were carried out mostly in northern Iraq, defense officials said, but they did not say where each leader was killed.

The attacks came amid a wider effort to pile pressure on the IS group before a major counter-offensive in coming months and as Kurdish forces made gains against the militants around Sinjar near the Syrian border.

US officials named three figures who were killed in the targeted raids, and said other “mid-level” leaders also were taken out.

The most significant figure was identified as Haji Mutazz, better known as Abu Muslim al-Turkmani, who was deputy to the group’s chief, Abu Bakr al-Baghdadi.

Pentagon officials said a second senior militant, referred to as Abd al Basit, also was killed, and was believed to be overseeing the group’s military operations.

In addition, a third militant, known as Radwin Talib, described as a “mid-level” figure overseeing the captured city of Mosul, was killed at some point after mid-September, officials said.

The Wall Street Journal first reported that US forces had taken out several key leaders, quoting the military’s top officer, General Martin Dempsey.

“These are high-value targets, senior leadership,” Dempsey told the Journal.

The newspaper, quoting unnamed officials, said between December 3 to December 9, air raids killed Basit and Turkmani.

The United States launched air strikes against the IS group on August 8 in Iraq, and expanded the raids to Syria on September 23. A coalition of Western and Arab countries has joined the US-led air campaign, which focused this week on IS militants around Sinjar.

Manhunts against senior leaders has become a common tactic in Washington’s war against Al-Qaeda and affiliated extremists over the past decade.

Since the attacks of September 11, 2001, US intelligence agencies repeatedly targeted senior leaders in drone air strikes in Pakistan and the American military conducted frequent raids on the ground and in the air against senior insurgents in Iraq and Afghanistan.